Showing two pictures of a side view of Cisna, one with his stomach bulging over his shorts, it's easy to see Cisna’s changed physique.

The teacher challenged his students to help him figure out appropriate daily nutritional limitations of 2000 calories and hitting recommended daily allowances of things like carbs and fats, KFOR said.

In addition to eating the McDonald’s meals, Cisna started walking 45 minutes every day.

“I tell people not only can I see my shoes now, but I can actually tie them,” Cisna told KFOR.

Cisna typically started his day with two egg white delights, a bowl of maple oatmeal, and 1 percent milk, KFOR said. Lunch was usually a salad but dinner was a meal of some kind.

“So this isn’t something where you say, ‘Well he went to McDonald’s and he only had the salads,’” Cisna told KFOR. “No, I had the Big Macs, the Quarter Pounders with cheese, I had sundaes, I had ice cream cones.”

A local McDonald’s manager agreed to give the teacher his meals for free to see where this experiment would lead.

Cisna, 54, was interviewed on the "Today" show Monday and told hosts there that while everyone was paying attention to how much weight he lost, he was more impressed with his blood cholesterol levels going down. “I knew I was going to lose weight,” Cisna told Today. “Math tells you that if you only eat 2000 calories a day, your body has to use more calories than that just to operate.”